1. Field of the Invention
The present invention relates to an optical component and an electronic board that have a low coefficient of linear expansion and small mold shrinkage, a method for producing the optical component, and a method for producing the electronic board.
2. Description of the Related Art
Plastics that are light-weight and easy to mold are useful for forming optical components (lenses, mirrors, etc.) and electronic boards (printed boards etc.). These optical components and electronic boards are expected to be used in various temperature environments during production and use. Thus, materials that do not readily undergo thermal deformation, in other words, materials that have low coefficients of linear expansion and do not significantly shrink during molding are desired.
In general, in the field of optical components, cyclic olefin polymers are used in optical components such as lenses since cyclic olefin polymers have a low water absorbing property and high transparency. In the field of electronic boards, resins such as polyimides having high heat resistance are mainly used in printed boards and substrates for mounting semiconductors.
However, in order for materials to be used in high precision optical components that realize high resolution and in electronic boards with a significantly high degree of integration, the coefficient of linear expansion is desirably low. In particular, cyclic olefin polymers have high coefficients of linear expansion and the usage thereof is significantly limited. In contrast, polyimides have significantly low coefficients of linear expansion but poor moldability and thus usage of the polyimides has been limited.
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 46, p. 2799 to 2806 (2008), “Styrene 4-Vinylbenzocyclobutene Copolymer for Microelectronic Applications” reports that the glass transition temperature (Tg) and the heat resistance improved in a thin film having a thickness of 4 μm obtained by crosslinking a copolymer of vinylbenzocyclobutene and methyl methacrylate.
Japanese Patent Laid-Open No. 2005-280261 discloses a polymer composed of a polyfunctional (meth)acrylate compound and reports that a molded article that has a low coefficient of linear expansion can be produced.
However, the coefficient of linear expansion disclosed in the aforementioned monograph in Journal of Polymer Science does not satisfy the recent requirement of high performance for use in optical components and electronic boards and thus the usage of the material is limited. Moreover, the polymer disclosed in the monograph in Journal of Polymer Science described above has many limitations as to the methods for molding although favorable coefficients of linear expansion are obtained owing to the (meth)acrylate compound. Moreover, the mold shrinkage caused by polymerization of (meth)acryl groups is significantly large and the material is difficult to use in optical components and electronic boards.
The present invention provides an optical component and an electronic board that have a low coefficient of linear expansion and small mold shrinkage.